1. Field of the Invention
The invention relates to pour point depressants and their use as flow parameters for oils, particularly paraffin-containing crude oils. The composition comprises polyolefins which have been modified by at least one side chain to the olefin monomer backbone.
2. Statement of the Related Art
As a result of the recent shortage of crude oil, there was a steady increase in the production and processing of petroleum crude oils having a relatively high content of paraffin hydrocarbons which are solid at room temperature. Oils such as these lose their fluidity on cooling from the higher temperature of the reservoir to ambient temperature through the crystallization of relatively high-melting constituents. In order, therefore, to avoid difficulties during production, transport and processing, "fluidity promoters," also known as "crystallization inhibitors," "flow promoters," and "pour point depressants" (see below), are added to the crude oil in the warm state in which it accumulates at the well, i.e., in a state in which the paraffin is still dissolved in the crude oil. The flow promoters used are generally polymers. They prevent the formation of relatively large aggregations of paraffin crystals and, in doing so, improve the fluidity of the crude oil. This is accompanied by a reduction in the pour point. The pour point is the temperature at which the crude oil is fluid as defined by a standard method. Accordingly, flow promoters are also generally known as pour point depressants and are characterized by the reduction which they bring about in the pour point.
Several such products are already known. U.S. Pat. Nos. 3,904,385 and 3,951,929 and corresponding published German patent application No. 22 64 328 describe the use of poly(n-alkyl)acrylate containing from 18 to 24 carbon atoms in the alcohol function. One of the disadvantages of these products is that they have to be used in relatively high concentrations of from 0.01 to 3% by weight, based on the weight of crude oil. Another disadvantage is that the stock solutions of the flow promoters themselves, usually 30 to 50% solutions in toluene, are impossible or very difficult to handle at ambient temperatures around freezing point or lower.
The same disadvantage also applies to the products described in British Pat. No. 2,125,805 and corresponding published German patent application No. 32 26 252, i.e., esters of (meth)acrylic acid with long-chain alcohols which have been chain-extended by reaction with ethylene oxide and/or propylene oxide. Although these products lower the pour point even when used in very small quantities, their solutions are virtually impossible to process at temperatures below about 0.degree. C.
Some rection products of epoxide polybutadienes are already known and used in unrelated industries. Thus, published German patent application No. 34 42 200 and corresponding U.S. patent application No. 799,536 filed Nov. 19, 1985, (which is incorporated herein by reference and the patent rights to which were commonly assigned with the subject invention effective their respective conception dates), describe air-drying lacquer binders in the form of reaction products of epoxidized polybutadienes with: unsaturated C.sub.6-22 carboxylic acids; or with alcohols having a functionality of from 2 to 6 which are then reacted in a following step up to an OH number below 25 by esterification with unsaturated C.sub.6-22 carboxylic acids. The compounds disclosed in the foregoing have only unsaturated side chains, which is to be expected since their disclosed utility is for air drying laquer binders. Unsaturated side chains would also be substantially less desirable for pour point depressants, a utility disclosed below for the present invention.
It is standard practice with pour point depressants based on (meth)acrylates to produce the monomers by azeotropic esterification in toluene or xylene and also to polymerize them in those solvents, in contrast with those of the present invention which can be produced without using solvents, as well be discussed below.